Device for operating a door, gate valve or similar closing means



Feb. 23, 1960 D. VAN DONGEN DEVICE FOR OPERATING A DOOR. GATE VALVE OR SIMILAR CLOSING MEANS Filed March 27. 1953 3 Sheets-Sheet l 1N VENTOR w 8 E 04 N M m D n N N-M m 1 m M C 3 0 a I Dwm Feb. 23, 1960 D VAN DQNGEN 2,926,013

DEVICE FOR OI ERATING A DOOR, GATE VALVE OR SIMILAR CLOSING MEANS Filed March 27. 1953 3 Sheets-Sheet 2 INVENTOR Din/3c mmrv Va Don ew BY SJGA m d-[ATTORNEYS Feb. 23, 1960 VAN DQNGEN 2,926,013

DEVICE FOR OPERATING A DOOR, GATE VALVE 0R SIMILAR CLOSING MEANS Filed March 27. 1953 3 Sheets-Sheet 3 F JO INVENTOR fliflyeman 26a flan en/ BY PM W Wi/LVL L4 ATTORNEYS United States Patent DEVICE FOR OPERATING A DOOR, GATE VALVE OR SIMILAR CLOSING MEANS Dingeman Van Dongen, Haarlem, to N.V. Bronswerk, Amersfoort, ration of the Netherlands Application March 27, 1953,-Selial No. 344,999

Netherlands, assignor Netherlands, a corpo- The invention refers to the operation of a door, gate, valve or similar closing device, particularly a fire door.

Several devices are known already for automatically closing a door or similar closing device which due to another cause has been brought into the open position. These devices generally consist of spring hinges or gravity hinges.

One of the disadvantages of these known devices consists in that the closing device only can be moved in one direction and that the movement in the opposite direction has to be eifected by hand or by some other exterior force.

If these known devices must be used for closing under certain conditions a closing device which is normally open, this closing device must be retained in its open position by a locking device which is not connected with the closing mechanism so that this locking device first has to be unlocked by hand or in some other way.

Another disadvantage of these known devices consists in that only a very small closing force acts upon the closing device and that also a very small force keeps the closing device in its closed position so that the latter also can be somewhat opened again by a very small force if it is not locked. This is particularly difficult in the case of fire doors on board ships which, owing to the movements of the vessel, often must rotate around an axis which is not vertical and in the case of doors or gates on which for instance the wind can exercise an influence and thus hamper or prevent its closing. In this way it may happen that such a closing device closes itself insufiiciently or even does not close itself at all.

The present invention avoids these difliculties'in that the device is provided with an element of variable length, one end of which is hingingly connected to a rotatable arm whilst the other end has a fixed centre of rotation situated outside the line limited by the centre of rotation of the rotatable arm and the point of articulation between this arm and the said element.

Further particulars and characteristics of the invention will be discussed below with the aid of the accompanying drawings, wherein;

Fig. 1 is a diagrammatic indication of the principle underlying the invention.

. Fig. 2 is an embodiment of the device according to the invention applied to a self-closing door.

Fig. 3 diagrammatically shows the arrangement relative to each other of the centres of rotation according to Fig. 2.

Fig. 4 is a longitudinal sectional view of the element of variable length.

Fig. 5 diagrammatically shows some special positions of the closing device.

, Fig. 6 is a diagrammatic drawing in perspective of the device according to the invention.

Fig. 7 is a top-view of the locking devices provided in the closing device.

Fig. 8 is a front-view of the corresponding locking devices provided in or to a fixed wall.

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Fig. 9 is a vertical sectional view of the unlocking mechanism.

Fig. 10 is a sectional view of the control valve for the supply and discharge of the pressure medium.

From Fig. 1 it may be seen that the device consists mainly of a rotatable arm located between 1 and 2 and of fixed length which has a centre of rotation at 1. An element located between 2 and 3 is rotatably secured to this arm at 2 which element can be shortened or lengthened by the device 4. The element 2, 3 has a fixed centre of rotation at 3.

If one wishes to have the triangle 1, 2, 3 rotate around the centres of rotation 1 and 3 then it is necessary for the leg 2, 3-which, if it would retain the same length, would describe the arc 2, 5to be shortened to the leg 2, 3, should a rotation be possible. On the other hand the triangle can also be rotated by exciting in the device 4' a force K which tries to shorten the leg 2, 3. For it is that this force K can be decomposed into a component R, which acts along the leg 1, 2' and which is absorbed by the point of articulation 1, as well as in a force T tangential to the are 2, 6 to be described by the point 2, the device being brought into a rotating movement by the said components T.

Fig. 2 shows an embodiment of the invention for a door 18 which can be rotated over 180 by means of a pressure medium. The drawn embodiment refers more in particular to a fire door which in the drawn position and in a position at an angle of more than therewith is locked in open condition and which in a position between these two open positions is locked in closed condition.

Quite in accordance with Fig. l the centres of rotation of the device have been given again the reference numbers 1, 2 and 3 whilst the element of variable length is also indicated by 4. The centres of rotation 1 and 3 are fixedly provided on a hinge plate 7 which is fixedly secured to a wall 8. Fig. 3 diagrammatically shows the arrangement of the centres of rotation .1, 2 and 3 as well as of the wall 8.

The element 4 of variable length is shown in Fig. 4 in a longitudinal sectional view. It consists of a cylinder 4 constituted by two aligned and communicating spaces 9 and 10 of different diameter. In this cylinder a T-shaped piston 11, 12 is provided in such a way that its thinner portion 11 closely fits into the narrower portion of the cylinder whereas the thicker portion 12 of the piston closely fits into the wider portion 10 of the cylinder. A connecting rod .13 is secured to the piston head 12, which connecting rod projects through the cylinder whilst hermetically fitting in the packing gland 14, the other end of the connecting rod being hingingly connected at 2 with the rotatable arm 1, 2 (Fig. 2). If a pressure medium is supplied through the line 15 above the head 12 of the piston then this piston will move in the drawing towards the left so that the device and therefore the door-as explained above-will start rotating. The medium in the space 10 is consequently forced out through the line 16. The space 9 contains air which is compressed below the thin portion 11 of the piston. If the air pressure in the space 9 exceeds a certain value a spring-biassed blow-off valve 17 opens and consequently the air pressure in this space 9 remains at a constant maximum preadjustable value. tion, rotates at a constant speed which prevents its clapping into the closed position with an undesirable force.

For rotating the closing device in the opposite direction the supply of the pressure medium is switched from the line 15 to the line .16 by means of a control valve to be described below. Consequently a pressure is produced in the space 10 due to which the piston in the drawing is moved towards the right, the pressure medium in the space above the piston head 12 flowing away through the line 15 and the control valve.

Consequently the door, after an initial accelera-- During this return movement the action of thepressure in the space '10 is at first intensified by the compressed air in the space 9. However, as during the preceding compression of this air part thereof has been blown off through the valve 17 a pressure of 1 at. will prevail again in the space 9 long before the piston has finished its entire stroke towards the right. When the movement of the.

piston towards the right is continued, an under pressure will be produced in the space 9 which will restrict the speed of movement. The magnitude of this under pressure is also limited by a spring biased inlet valve 17, as shown in Figure 4, which opens at a preadjustable value of the under pressure and allows air to leak in. In this way the reverse movement also will takeplace at a uniform and controlled speed, after an initial acceleration.

The above-mentioned control valve 19 (Figs. 2 and 6) is secured to the cylinder or to a portion of the device fixedly secured therewith as near as possible to or coinciding with the axis of rotation thereof, so that the lines 15 and 16 may be of rigid construction. The supply and discharge of the pressure medium to and from this control valve is effected according to any known, flexible and/or rotatable connecting system.

Fig. shows a sectional view of the above-mentioned control valve. It consists of a housing 20 which in the case of the embodiment shown is constructed as a hinge of the door 18 and the device of variable length 4, the housing 20 forming one knuckle of a hinge which is hingedly attached to the hinge plate 7 that forms the other knuckle 4 is secured to the Wall 8. In this housing 20 the cylinder 21 of the control valve is rotatably mounted so that this cylinder can remain stationary when the housing 20 rotates. The supply line 15, shown in Fig. 4, for the pressure medium is connected to the cylinder 21 which supply line continues into the passage 22 through the cylinder and the passage 23 through the valve 24 whilst finally terminating at the point 25 on the periphery of the valve. The valve 24 is provided with four enlarged portions 26, 27, 28 and 29 which closely fit into the central perforation of the cylinder 21. In this way annular spaces are formed between each two of these enlarged portions, these spaces being indicated by 30, 31 and 32 respectively. Below the valve 24 a helical spring 33 is provided keeping the valve in its extreme uppermost position. In this position the mouth 25 of the supply passage for the pressure medium in the space 31 corresponds with the supply passages 34 and '35 in the cylinder whilst the passage 36 is closed by the enlarged portion 27. The passage 34 terminates in an annular groove 37 provided in the cylinder. Through this annular groove the passage -which so conveys a pressure medium to the element of variable length that the dooris closedalways communicates with the passage 34 independent of the position of the door.

When the piston in the cylinder 4 of the element of variable length moves. towardsthe right in the drawing owing to the supply of the pressure medium through the line 15, the medium present at the other side of the piston in the cylinder 4 is discharged through the line 16, the annular groove 38, the passage 39, the annular space 32 and the passage 40. In this position the passage '41 of the supply line 42 is closed by the enlarged portion 23 of the valve 24.

If the movement of the piston in the cylinder 4 must be reversed and the pressure medium musttherefore be supplied to the cylinder through the line 16 and discharged through the line 15, then the valve 24 is moved downwards against the action of the spring 33. Consequently the mouth 25 of the passage 23 is placed opposite the passage 39 and is brought in this way in communication with the passage 16. At the same time the mouth of the passage 39 at the annular space 32 is closed by the enlarged portion 28 so that the pressure medium supplied cannot flow away immediately through the discharge passage 40. When the valve 24 moves downwards the enlarged portion 27 is placed opposite the mouth of the passage 34 whilst the mouths-of-the passages36 and 43'com-- municate with the annular space 30. The pressuremedium which is now forced out of the cylinder 4 through the lines 15, 34 and 36 enters in this way the annular space 30 and flows from this space through the passage 43 to the annular space 32 in order to he finally discharged from the control valve to the passage 40.

As is evident from the above this control valve is constructed in such a way that it is normally always in the position in which the pressure meditun is supplied to that,

side of the piston which enables the latter to move the door from one of its open positions into the closed position.

In order to make it possible that the device 18 (Fig. 2) is placed in its closed position hermetically fitting against the wall '8 and that at the same time it still can rotate over an angle of more than a spring-biased doorpost 44 is fixed to this wall so that it becomes even possible to rotate the door over since the inner side edge of the door will contact the door-post 44 instead of the wall and will be sealed thereby and yet will be able to move from a position in alignment therewith and still be in sealed contact therewith so that the door can be in a position out of a 90 angular relation with the wall 8 and still be sealed at its inner side edge by the post 44.

From the above it is evident that the device according to the invention in the position according to Fig, 2 and in the position making an angle of 180 therewith only exercises a small force on the door 18. If the latter has a large mass and/or if in its centres of rotation a large friction is caused, the force exercised by the piston will be insufficient to bring the door quickly out of the drawn position. In order to remove this difi'iculty a compression spring 45 has been provided between the device 18 and the fixed wall 8 which spring is under compression in the drawn position and will give the door 18 a starting impulse when unlocking'the latter so that it quickly is brought into a rotating movement.

The locking device according to the invention is executed in such a way that. the rotatable member can be locked in any position independent of the direction in which the rotating member moves towards that position. As shown in Figs. 6, 7 and 8 two superimposed lock bolts 49 and 50 are fixed for this purpose to the freely rotating end of the closing device. These look bolts are so arranged that their rounded off or chamfered portions point towards two opposite sides of the closing device 18. When the device is locked these two lock bolts shoot into two horizontally arranged U-shaped recesses 51 and 52 provided one above the other at distances corresponding with the lock bolts in the other half of the locking device (Fig. 8). The open end of each of these U- shaped recesses is so arranged that in the locking position it points to the same side of the rotatable device 13 as the rounded ofi or chamfered portion of the lock bolt resting in this recess. Moreover, the recesses overlap each other in a horizontal direction over a distance a (Fig. 8) which substantially corresponds with the thicknesses a (Fig. 7) of the lock bolts to be received therein. In this way one obtains that the rotatable device 18 is locked towards both sides without clearance of any importance being caused in the locking, whereas on the other hand the lock bolts can enter the recesses 51, 52 independently of the direction of rotation of the rotating device and without the necessity of moving the handles for this purpose.

Each of the lock bolts 49 and 50 can be operated by a handle 53 and 54 which is known per se, said handles being interconnected by a hinging connecting rod 55 so that by moving one of the four handles both lock bolts 49and 50 are unlocked and the device 18 can be rotated. This pushing down of the handles can be done by hand or by means of a plunger 56 of the piston 57 in a cylinder 58 (Fig. 9). Under the piston 57 a helical spring 59 has been provided around the plunger 56 so that the plunger is pushed upwards-and is kept-out ofwcontact with the handle 53. If the device according to the invention must be moved out of one of its open positions, the pressure medium brought into the cylinder 4 also flows through the line 60 to the space in the cylinder 58 above the piston 57 so that the plunger 56 moves downwards and the handles 53 and 54 are so rotated that the lock bolts 49 and 50 are unlocked from the recesses 51 and 52 and consequently the device 18 can start rotating. Due to the fact that the cylinder 58 is secured to a fixed portion, for instance to a wall 8, and that further the lower end of the plunger 56 has a spherical shape the handle 53 will be freed from the plunger 56 already after a very small movement of the device 18 and will rotate back into its 01f position. In this Way the lock bolts 49 and 50 resume such a position that for the purpose of locking the device 18 in its closed position they can engage a second set of recesses 51 and 5 2.

As is evident from the above description the rotating device 18 is pushed with great force by the pressure medium used into its closed position and is locked therein. If the rotatable device consists for instance of a fire door it may be desirable to open same temporarily in order to give somebody trapped in the burning section the chance to escape therefrom. However, as it is not possible or only very difficult to re-open the fire door against the pressure of the medium a device is provided by means of which this opening is efiected by the pressure medium itself as soon as the door is unlocked by depressing orie of the handles 53 or 54. For this purpose it is necessary that the control valve 19 is brought in such a position that the supply of the pressure medium to the line 15 is interrupted and is switched over to the line 16. To this end an arm 61 is fixedly secured to the shaft connecting the two handles 53, which arm, as may be seen from Fig. 9, is taken along downwards if pressure is exerted on one of the handles 53 or 54. To the arm 61 a cable, rope or a similar flexible means 62 is attached which is so connected via some guide pulleys with the control valve 19 that the latter is brought into the desired position, the pressure medium being conveyed through the line 16. Therefore, if the handles of the closed door are moved downwards the action of the lever 61, the cable 62 and the control valve 19 will cause the pressure medium to be conveyed through the line 16 to the space in the cylinder 4, so that the piston 11 starts moving towards the right and the door 18 is opened. However, as soon as the handles are released, these will move upwards with the lever 61 so that the control valve is readjusted in such a way that it now conveys the pressure medium again through the line and the piston is moved toward the left which results in the door reclosing automatically.

Fig. 5 shows diagrammatically how a rotatable member according to the invention can be provided for instance in a passage in such a way that it can be opened in the position 63 as well as in the position 64 whereas a position 65 indicates the closed position. On the other band also one of the positions 63 or 64 can indicate the closed position in which case the position 64 or 63 respectively shows the open position.

If the device according to the invention is used for automatically closing a fire door, it is preferable to combine it with an automatic fire extinguishing device such as a sprinkler installation. Such installations are usually permanently under the pressure of some medium which is undesirable for the present device, since in this way all kinds of parts would be continually subjected to a great force and moreover the unlocking device 5660 would come into action. In order to avoid this ditficulty the device according to the invention is connected to the pressure line of the fire extinguishing installation by means of a balancing valve which allows the pressure medium to pass to the control valve 19 only after a decline of pressure has taken place in the pressure line of the fire extinguishing installation. However, as the construction of such a-balancing valve does not form part of the present invention it will not be further explained.-

I claim:

1. A fluid pressure opening and closing device for operating a rotatable closing member which is hingedly fixed by a hinge connection to a fixed supporting structure and is rotatable relative thereto; said device comprising a cylinder, a piston therein and having a rod extending through one end of the cylinder, said cylinder being fixedly attached to the closing member in such a way that the outer end of the piston rod protruding from the cylinder is pointing away from the axis of rotation of the rotatable closing member and is movable in a rectilinear direction perpendicular to the axis of rotation of the rotatable closing member, an arm of fixed length hingedly attached at one end to the end of the piston rod, the other end of said arm being pivotally mounted at a fixed point on the supporting structure independent of the hinge connection for the closing member and laterally outside a vertical plane through the hinge connection for the closing member and the hinge connection between the piston rod and the arm of fixed length, latching means on said closing member, a first securing means cooperating with the latching means for holding the closing member in its closed position, a second securing means cooperating with the latching means for holding the closing member in its opened position, operating means for said latching means, means for discharging a pressure medium from the cylinder in a way to retard the movement of the piston in the cylinder, a two-way control valve for the supply of a pressure medium to the cylinder, spring means urg'mg the valve to one position and means actuated by the operating means for the latching means for moving the valve to its other position in opposition to the spring means.

2. A fluid pressure opening and closing device for operating a rotatable closing member which is hingedly carried by and rotatable relative to a fixed supporting structure, said device comprising a cylinder, a piston working therein and having a rod extending through one end of the cylinder, said cylinder assembly being fixedly attached to the closing member in such a way that the end of the piston rod protruding from the cylinder is movable in a rectilinear direction perpendicular to the axis of rotation of the rotatable closing member, an arm of fixed length hingedly attached at one end to the end of the piston rod, the other end of said arm being pivotally mounted at a fixed point on the supporting structure independent of and spaced from the hinge connection for the closing member, latching means on said closing member, a first securing means cooperating with the latching means for holding the closing member in its closed position, a second securing means cooperating with the latching means for holding the closing member in its opened position, handle means for said latching means, means for discharging the pressure medium from the cylinder in a way to retard the movement of the piston in the cylinder, a two-way control valve for the supply of a pressure medium to the cylinder, spring means for normally urging the valve to one position and means actuated by the handle means for moving the valve to its other position in opposition to the spring means.

3. A fluid pressure opening and closing device for operating a rotatable closing member which is hingedly carried by and rotatable relative to a fixed supporting structure; said device comprising a cylinder, a piston working therein and having a rod extending through one end of the cylinder, said cylinder assembly being fixedly attached to the closing member in such a way that the end of the piston rod protruding from the cylinder is movable in a rectilinear direction perpendicular to the axis of rotation of the rotatable closing member, an arm of fixed length hingedly attached at one end to the end of the piston rod, the other end of said arm being pivotally mounted at a fixed point on the supporting structure independent of and spaced from the hinge connection for the closing member, latching means on said closing member, a first securing means cooperating with the latching means for holding the closing member in its closed position, a second securing means cooperating with the latching means for holding the closing member in its opened position and handle means for said latching means, a two-way control valve for the supply of a pressure medium to the cylinder, spring means normally urging the valve to one position and means actuated by the handle means for moving the valve to its other position in opposition to the spring means, said handle means being controlled by a control member, spring means normally retaining said control member out of contact with the handle means and power means for moving the control member into contact with the handle means.

4. A fluid pressure opening and closing device for operating a rotatable closing member which is hingedly carried by and rotatable relative to a fixed supporting strucutre; said device comprising a cylinder, a piston working therein and having a rod extending through one end of the cylinder, said cylinder assembly being fixedly attached to the closing member in such a Way that the end of the piston rod protruding from the cylinder is movable in a rectilinear direction perpendicular to the axis of rotation of the rotatable closing member, an arm of fixed length hingedly attached at one end to the end of the piston rod, the other end of said arm being pivotally mounted at a fixed point on the supporting structure independent of and spaced from the hinge connection for the closing member, latching means on said closing member, a first securing means cooperating with the latching means for holding the closing member in its closed position, a second securing means cooperating with the latching means for holding the closing member in its opened position and operating means for said latching, means for discharging a pressure medium from the cylinder in a way to retard the movement of the piston in the cylinder, a two-way valve for the supply of a pressure medium to the cylinder, spring means normally urging the valve to one position, means actuated by the operating means for the latching means for moving the valve to its other position in opposition to the spring means, said operating means for the latching means being controlled by a control member, spring means normally retaining said control member out of contact with the operating means and power means for moving the control member into contact with the operating means.

5. A fluid pressure opening and closing device for operating a rotatable closing member which is hingedly carried by and rotatable relative to a fixed supporting structure; said device comprising a cylinder, a piston working therein and having a rod extending through one end of the. cylinder, said cylinder assembly being fixedly attached to the closing member in such a way that the end of the piston rod protruding from the cylinder is movable in a rectilinear direction perpendicular to the axis of rotation of the rotatable closing member, an arm of fixed length hingedly attached at one end to the end of the piston rod, the other end of said arm being pivotally mounted at a fixed point on the supporting structure independent of and spaced from the hinge connection for the closing member, latching means on said closing member, a first securing means cooperating with the latching means for holding the closing member in its closed position, a second securing means cooperating with the latching means for holding the closing member in its opened position and handle means for said latching means, means for discharging the pressure medium from the cylinder in a way to retard the movement of the piston in the cylinder, a two-way control valve for the supply of a pressure medium to the cylinder, spring means for normally urging the valve to one position and means actuated by handle means for moving the valve to its other position in opposition to the spring means, the

handle means being controlled by a control member, spring means normally retaining said control member out of contactwith the handle means and power means for moving the control member into contact with the handle means.

6. A fluid pressure opening and closing device for operating a rotatable closing member which is hingedly mounted by a hinge connection to a fixed supporting structure and is rotatable relative thereto, said device comprising a cylinder, a piston Working therein and having a rod extending through one end of the cylinder, said cylinder being fixedly attached to the closing member in a position so that the outer end of the piston rod protruding from the cylinder is pointing away from the axisof rotation of the rotatable closing member and is movable in a rectilinear direction perpendicular to said axis of rotation of the rotatable closing member, and arm of fixed length hingedly attached at one end to. the outer end of the piston rod, the other end of said arm being pivotally mounted at a fixed point on the supporting structure independent of the hinge connection for the closing member and laterally outside a vertical plane through the hinge connection for the closing member and the hinge connection between the piston rod and the arm of fixed length.

7. A device as claimed in claim 6, further including means for discharging a pressure medium from the cylinder in a way to retard the movement of the piston in the cylinder.

8. A device as claimed in claim 6, further including a two-way control valve for the supply of a pressure medium to the cylinder, spring means urging the valve to one position and means actuated by handle means for moving the valve in its other position in opposition to the spring means.

9. A fluid pressure opening and closing device for operating a rotatable closing member which is hingedly carried by and rotatable relative to a fixed supporting structure, said device comprising a cylinder, a piston working therein and having a rod extending through one end of the cylinder, said cylinder assembly being fixedly attached to the closing member in such a way that the end of the piston rod protruding from the cylinder is pointing away from the axis of rotation of the rotatable closing member and is movable in a rectilinear direction perpendicular to said axis of rotation of the rotatable closing member, an arm of fixed length being hingedly attached at one end to the end of the piston rod, the other end of said arm being pivotally mounted at a fixed point on the supporting structure independent of the hinge connection for the closing member and laterally outside a vertical plane through the hinge connection for the closing member and the hinge connection between this piston rod and the arm of fixed length, means for discharging a pressure medium from the cylinder in a way to retard the movement of the piston in the cylinder, a two-way control valve for the supply of the pressure medium to the cylinder, spring means urging the valve to one position, a handle means, and means actuated by they handle means for moving the valve in its other position in opposition to the spring means.

10. A fluid pressure opening and closing device for operating a rotatable closing member which is hingedly fixed by a hinge connection on a fixed supporting structure and is rotatable relative thereto, said device comprising a cylinder, a piston working therein and having a rod extending through one end of the cylinder, said cylinder being fixedly attached to the closing member in a position so that the outer end of the piston rod protruding from the cylinder is pointing away from the axis of rotation of the rotatable closing member and is movable in a rectilinear direction perpendicular to said axis of rotation of the rotatable closing member, an arm of fixed length hingedlyattached at one end to the outer end of the piston rod, the other-end-of-said arm-being pivotally mounted at a fixed point on the supporting structure independent of the hinge connection for the closing member and laterally outside a vertical plane through the hinge connection for the closing member and the hinge connection between the piston rod and the arm of fixed length, means for discharging a pressure medium from the cylinder in a Way to retard the movement of the piston in the cylinder, a two-way control valve for the supply of the pressure medium to the cylinder, spring means urging the valve to oneposition, a handle means, means actuated by the handle means for urging the valve to one position and means actuated by the handle means for moving the valve in its other position in opposition to the spring means, a control member controlling the handle means, spring means retaining said control mem- 15 2,586,442

her out of contact with said handle means and power means for moving the control member into contact with the handle means in opposition to the last-named spring means.

References Cited in the file of this patent UNITED STATES PATENTS 887,530 Scott et al May 12, 1908 1,859,364 Haskell May 24, 1932 1,938,502 Steindler et a1 Dec. 5, 1933 2,091,338 Dorsey Aug. 31, 1937 2,190,653 Dunn Feb. 20, 1940 2,243,914 Martin June 3, 1941 2,301,950 Hulse Nov. 17, 1942 Seagren Feb. 19, 1952. 

